The UK's road and rail networks criss-cross one another at thousands of points - the collision at Manningtree highlights the potential dangers of this close proximity.

Almost any car journey involves some interaction with the UK's complex web of railway lines - be it a tunnel under the track, a bridge over the lines or the negotiating of a level crossing.

Keeping road vehicles and trains safely apart has been a problem since the birth of the railway. The fatal derailment of two trains near Selby, caused by a car falling onto the tracks, was a reminder that danger still exists.

At least 13 people were killed in the Selby crash

Following the crash, the Highways Agency set up a working group to review the use of nearside safety barriers on major roads in the UK.

But the age of our railway infrastructure, and the rise in road traffic, means potential hazards are numerous, particularly at level crossings.

Addressing these trouble spots is an expensive proposition, says Dr Ralph Harrington of the Institute of Railway Studies.

"It's a big investment. We have a legacy of reconstruction and something is being done, but it costs money and is not a priority."

The safety systems developed by rail operators to manage this hazardous sharing of space are heavily regulated and scrutinised, but an equal responsibility for safety rests with each and every motorist, says Dr Harrington.

"The behaviour of road users is the major issue. The actions of drivers tends to be the cause of many of the incidents where the two modes of transport enter the same sphere."

Road bridges

Cases of motor vehicles leaving a carriageway at a railway line are rare, says Dr Harrington.

"Parapets are built to a defined British standard and specifically designed to prevent a vehicle leaving the road. They are tested and regularly inspected."

A bridge barrier's job is two-fold; to absorb the energy of an impact, slowing the crashing vehicle; and shepherd it along - rather than off - the carriageway.

"A lot of care is taken to ensure these parapets only receive a glancing impact. They are curved or bent around at the ends so that any impact comes at an obtuse angle. It is almost impossible to hit these barriers head-on."

However, no system is infallible. In 1998, a lorry driver taking a "short cut" hit the stone parapet of a bridge over Scotland's busiest inter-city lines - showering masonry onto the track and slightly damaging one train.

Of course, barriers are only present on bridges themselves and the run-up to them. It is still possible for vehicles to leave the road before the barriers begin.

Rail bridges

Even when road traffic passes under a train track, the behaviour of motorists can still spark a potential disaster.

Last year, so-called "bridge strikes" were at their highest level for almost a decade, with 1,640 vehicles hitting rail bridges, according to Her Majesty's Railway Inspectorate.

More bridge strikes are being reported

Despite efforts to ensure these structures can withstand such punishment, three of last year's impacts were described as "serious".

"The authorities take a very serious view of this issue," says Dr Steedman. "Even old bridges will have been checked to ensure they can absorb the energy of a traffic strike without the collapse of the structure."

Angered by a spate of such collisions - each costing upwards of £500 to investigate - rail authorities in Scotland issued "truckers' maps" in a bid to prevent lorry drivers attempting to navigate structures too narrow or low for their vehicle.

Level crossings

Allowing road vehicles and trains to share the very same space is perhaps the greatest cause for concern, says Dr Harrington.

The nation's 8,228 level crossings were the scene of 32 "incidents" last year, and the site of 13 deaths.

In harm's way: level crossings can be dangerous

While some critics have blamed this death toll on the introduction of automated level crossing barriers, again it seems the recklessness of drivers is often more to blame.

The UK's most dangerous level crossing can be found at Ardrossan in Aryshire. In two years, train drivers reported 25 "near-misses".

In an attempt to understand the problem, railway officials monitored vehicle behaviour at this notorious crossing, along with several others.

At Cornton in Sterling, 61 "misses" were observed in just nine days. Drivers ignored red signals and raced the closing gates, while one lorry even hit the barrier.

Cameras have been introduced in the hope of curbing such habits and preventing catastrophe.